UI: Fix drag & drop of files on main window

rpcs3/Emu/Cell/Modules/cellAudio.cpp

@@ -1019,6 +1019,13 @@ void cell_audio_thread::operator()()
 
 	// Destroy ringbuffer
 	ringbuffer.reset();
+
+	// Destroy the audio backend on this thread (the one that created it in cfg.reset()).
+	// The backend's ctor calls CoInitializeEx here on Windows; releasing it on a different
+	// thread (g_fxo->clear() runs on the GUI thread during Kill()) would land the matching
+	// CoUninitialize on the GUI thread, draining its OLE reference and silently breaking the
+	// main window's file drag&drop. Keep COM init/teardown balanced on this thread.
+	cfg.backend.reset();
 }
 
 audio_port* cell_audio_thread::open_port()

rpcs3/Emu/Cell/lv2/sys_rsxaudio.cpp

@@ -1413,6 +1413,20 @@ void rsxaudio_backend_thread::operator()()
 				{
 					lock.unlock();
 					backend_stop();
+
+					// Destroy the backend on this thread, the one that created it in backend_init().
+					// The backend's ctor calls CoInitializeEx here on Windows; if it is instead released
+					// by ~rsxaudio_backend_thread() (which runs on the GUI thread via g_fxo->clear()
+					// during Kill()), the matching CoUninitialize lands on the GUI thread, draining its
+					// OLE reference and silently breaking the main window's file drag&drop. Keep COM
+					// init/teardown balanced on this thread.
+					if (backend)
+					{
+						backend->Close();
+						backend->SetWriteCallback(nullptr);
+						backend->SetStateCallback(nullptr);
+						backend = nullptr;
+					}
 					return;
 				}
 

rpcs3/rpcs3qt/qt_music_handler.cpp

@@ -66,15 +66,24 @@ void fmt_class_string<QMediaPlayer::PlaybackState>::format(std::string& out, u64
 
 qt_music_handler::qt_music_handler()
 {
-	music_log.notice("Constructing Qt music handler...");
+	// Construct the QMediaPlayer on the GUI thread, the same thread on which it is destroyed
+	// (see ~qt_music_handler). cellMusic creates this handler from an emulated thread, but Qt's
+	// Windows multimedia backend balances its COM init/teardown per calling thread: constructing
+	// off the GUI thread and destroying on it left an unmatched CoUninitialize on the GUI thread,
+	// draining the OLE reference that Qt's startup OleInitialize set up until file drag&drop on
+	// the main window silently broke. Keeping both on the GUI thread keeps them balanced.
+	Emu.BlockingCallFromMainThread([this]()
+	{
+		music_log.notice("Constructing Qt music handler...");
 
-	m_media_player = std::make_unique<QMediaPlayer>();
+		m_media_player = std::make_unique<QMediaPlayer>();
-	m_media_player->setAudioOutput(new QAudioOutput(m_media_player.get()));
+		m_media_player->setAudioOutput(new QAudioOutput(m_media_player.get()));
 
-	connect(m_media_player.get(), &QMediaPlayer::mediaStatusChanged, this, &qt_music_handler::handle_media_status);
+		connect(m_media_player.get(), &QMediaPlayer::mediaStatusChanged, this, &qt_music_handler::handle_media_status);
-	connect(m_media_player.get(), &QMediaPlayer::playbackStateChanged, this, &qt_music_handler::handle_music_state);
+		connect(m_media_player.get(), &QMediaPlayer::playbackStateChanged, this, &qt_music_handler::handle_music_state);
-	connect(m_media_player.get(), &QMediaPlayer::errorOccurred, this, &qt_music_handler::handle_music_error);
+		connect(m_media_player.get(), &QMediaPlayer::errorOccurred, this, &qt_music_handler::handle_music_error);
-	connect(m_media_player->audioOutput(), &QAudioOutput::volumeChanged, this, &qt_music_handler::handle_volume_change);
+		connect(m_media_player->audioOutput(), &QAudioOutput::volumeChanged, this, &qt_music_handler::handle_volume_change);
+	});
 }
 
 qt_music_handler::~qt_music_handler()